Fluorine doped carbon films produced by modification by radicals

ABSTRACT

A film forming method includes the steps of forming a F-doped carbon film by using a source gas containing C and F, and modifying the F-doped carbon film by radicals, the source gas having a F/C ratio larger than 1 and smaller than 2, the F/C ratio being defined as a ratio of a number of F atoms to a number of C atoms in a source gas molecule.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a divisional of U.S. patent application Ser. No.10/567,733, filed Feb. 10, 2006, which is a National Stage Applicationof PCT Application No. PCT/JP2004/10484, to filed Jul. 23, 2004, andclaims priority to Japanese Patent Application No. 2003-293904, filedAug. 15, 2003. The entire contents of U.S. patent application Ser. No.10/567,733 are incorporated herein by reference in their entirety.

TECHNICAL FIELD

The present invention generally relates to method of forming insulationfilms and more particularly to a film forming method of a F(fluorine)-doped carbon film, fabrication method of a semiconductordevice that uses such a film formation method of fluorine-doped carbonfilm, a semiconductor device formed with such a method, and a substrateprocessing system for fabricating such a semiconductor device.

BACKGROUND ART

In recent miniaturized semiconductor devices, so-called multilayerinterconnection structure is used for electrically interconnecting avast number of semiconductor elements formed on a substrate. In amultilayer interconnection structure, a large number of interlayerinsulation films, each burying therein an interconnection pattern, arelaminated, and an interconnection pattern of one layer is connected toan interconnection pattern of an adjacent layer or a diffusion region inthe substrate via a contact hole formed in the interlayer insulationfilm.

With such miniaturized semiconductor devices, complex interconnectionpatterns are formed in the interlayer insulation film in closeproximity, and delay of electric signals caused by the parasiticcapacitance of the interlayer insulation film becomes a serious problem.

Thus, with the ultra-miniaturized semiconductor devices of these dayscalled submicron devices or sub-quarter micron devices, a copperinterconnection pattern is used as the interconnection layerconstituting the multilayer interconnection structure, and a F-dopedsilicon oxide film (SiOF film) having a specific dielectric constant of3-3.5 is used for the interlayer insulation film in place ofconventional silicon oxide film (SiO₂ film) having the specificdielectric constant of about 4.

However, there is a limit in the effort of reducing the specificdielectric constant as long as an SiOF film is used. With such aninsulation film based on SiO₂, it has been difficult to achieve thespecific dielectric constant of less than 3.0 as is required by thesemiconductor devices of the generation characterized by the design ruleof 0.1 μm or later.

Meanwhile there are various materials called low dielectric (low-K)insulation film having a low specific dielectric constant. On the otherhand, an interlayer insulation film used for the multilayerinterconnection structure is required not only to have a low specificdielectric constant but also high mechanical strength and high stabilityagainst thermal anneal processing.

A F-doped carbon (CF) film is a promising material for the lowdielectric constant insulation film for use in ultra fast semiconductordevices of the next generation in view of its sufficient mechanicalstrength and its capability of achieving low specific dielectricconstant of 2.5 or less.

Generally, a F-doped carbon film has a chemical formula represented byC_(n)F_(m). It is reported that such an F-doped carbon film can beformed by a parallel-plate type plasma processing apparatus or an ECRtype plasma processing apparatus.

For example, Patent Reference 1 obtains a F-doped carbon film by using afluorocarbon compound such as CF₄, C₂F₆, C₃F₈, C₄F₈, or the like, in aparallel-plate type plasma processing apparatus as a source gas.Further, Patent Reference 2 obtains a F-doped carbon film by using afluorinated gas such as CF₄, C₂F₆, C₃F₈, C₄F₈, or the like, in anECR-type plasma processing apparatus.

PATENT REFERENCE 1

Japanese Laid-Open Patent Application 8-83842

PATENT REFERENCE 2

Japanese Laid-Open Patent Application 10-144675

DISCLOSURE OF THE INVENTION Problems to be Solved by the Invention

In conventional F-doped carbon films, there has been a problem of largeleakage current. Further, there occurs degassing from the film when aconventional F-doped carbon films is heated to a temperature of about400° C., which is used in semiconductor process. Thus, the use of such afilm for the interlayer insulation film raises a serious problem ofreliability for the semiconductor device. Such large leakage current andoccurrence of degassing indicate that conventional F-doped carbon filmscontain various defects therein.

Further, when attempt is made to form such a F-doped carbon film byusing the conventional art, there is a need of adding a hydrogen gas tothe source gas in order to remove the F radicals formed as a result ofdissociation of the fluorocarbon compounds, while addition of suchhydrogen gas leads to the situation that the fluorine-doped carbon filmthus obtained contains a large amount of hydrogen therein. In such afluorine-doped carbon film containing large amount of hydrogen, however,there occurs release of HF in the film, while this leads to the problemof corrosion in the interconnection layer or in the insulation film.

Further, as noted before, an F-doped carbon film is used frequently in amultilayer interconnection structure as an interlayer insulation film incombination with copper interconnection patterns. With such a multilayerinterconnection structure that uses a copper interconnection pattern, itis essential to cover the sidewall surfaces of the interconnectiongrooves or via-holes, in which the interconnection patterns are formed,by a barrier metal film typically of Ta, or the like, in order to blockthe diffusion of Cu from the interconnection patterns. When a Ta barriermetal film is deposited on the surface of the F-doped carbon film,however, there occurs a reaction between F in the F-doped carbon filmand Ta in the barrier metal film and there is formed a volatile compoundof TaF. It should be noted that such formation of TaF occursparticularly on the sidewall surface of the via-holes where the F-dopedcarbon film is exposed, while formation of TaF causes degradation in theadherence and deteriorates the reliability or lifetime of the multilayerinterconnection structure.

FIG. 1 shows an example of the via-contact structure that uses such aconventional F-doped carbon film.

Referring to FIG. 1, there is formed an interlayer insulation film 2 ofan F-doped carbon film on a low-K dielectric interlayer insulation film1 in which a copper interconnection pattern 1A is embedded, whereinthere is formed a via-hole 2A in the F-doped carbon film 2 so as toexpose the copper interconnection pattern 1A while using a hard maskpattern 3 formed on the F-doped carbon film 2 as a mask.

On the sidewall surface of the via-hole 2A, there is exposed the F-dopedcarbon film constituting the interlayer insulation film 2, wherein theforegoing sidewall surface is covered with a Ta film 4 deposited on thehard mask pattern 3 so as to cover the via-hole 2A. With such a contactstructure, a large amount of hydrogen is contained in the film asexplained before, and there is a concern that F constituting the filmcauses a reaction with the hydrogen to form HF of corrosive nature.

Further, at the sidewall surface of the via-hole 2A in which the Tabarrier film 4 makes a contact with the fresh surface of the F-dopedcarbon film exposed by the dry etching process, there is formed avolatile TaF as a result of the reaction with F existing on such filmsurface.

Thus, it is the general object of the present invention to provide anovel and useful film forming method, fabrication method of asemiconductor device, semiconductor device and substrate processingsystem, wherein the foregoing problems are eliminated.

A more specific object of the present invention is to provide a filmforming method capable of forming highly reliable multilayerinterconnection structure while using a F-doped carbon film for theinterlayer insulation film.

According to the present invention, there is provided a film formingmethod, comprising the steps of:

forming a F-doped carbon film by using a source gas containing C and F;and

modifying said F-doped carbon film by radicals,

said source gas having a F/C ratio, defined as a ratio of a number of Fatoms to a number of C atoms in said source gas molecule, wherein saidF/C ratio is larger than 1 but smaller than 2.

Further, according to the present invention, there is provided a methodof fabricating a semiconductor device, comprising the steps of:

depositing a F-doped carbon film on a substrate by a plasma CVD processthat uses a source gas that contains C and F in a molecule thereof;

forming an opening in said F-doped carbon film by a dry etching processof said F-doped carbon film; and

covering a sidewall surface and a bottom surface of said opening by ametal film,

wherein there is provided, after said step of forming said opening butbefore said step of covering said sidewall surface and bottom surface ofsaid opening by said metal film, a step of modifying at least saidsidewall surface of said opening by radicals,

said source gas having a CF ratio, defined as a ratio of a number of Fatoms to a number of C atoms in said source gas molecule, wherein saidF/C ratio is larger than 1 but smaller than 2.

In another aspect, there is provided a substrate processing system,comprising:

a vacuum transfer chamber;

a first processing chamber coupled to said vacuum transfer chamber forconducing a dry etching of a fluorine-doped carbon film;

a second processing chamber coupled to said vacuum transfer chamber formodifying a fluorine-doped carbon film;

a third processing chamber coupled to said vacuum transfer chamber forconducting dry cleaning of a fluorine-doped carbon film; and

a fourth processing chamber coupled to said vacuum transfer chamber forconducting deposition of a metal film,

wherein each of said first and second processing chambers comprises:

a processing vessel coupled to an evacuation system and having a stagefor holding a substrate to be processed;

a microwave window provided so as to face said substrate to be processedon said stage and constituting a part of an outer wall of saidprocessing vessel;

a planar microwave antenna provided outside said processing vessel incoupling to said microwave window;

a first gas supply system for supplying a noble gas to an interior ofsaid processing vessel; and

a second gas supply system provided in said processing vessel so as todivide a space inside said processing vessel into a first space part inwhich said microwave window is included and a second space part in whichsaid stage is included, said second gas supply system being formed withan opening enabling invasion of plasma formed in said first space partinto said second space part.

In a further aspect, there is provided a method of fabricating asemiconductor device, comprising the steps of:

depositing a fluorine-doped carbon film on a substrate by a plasma CVDprocess that uses a source gas that contains C and F in a moleculethereof;

forming an opening in said fluorine-doped carbon film by a dry etchingprocess; and

depositing a first metal film so as to cover a sidewall surface and abottom surface of said opening,

wherein there is provided, after said step of forming said opening butbefore said step of depositing said first metal film, a step ofdepositing a second metal film that forms a stable compound when reactedwith F, such that said second metal film covers at least said sidewallsurface and bottom surface of said opening.

In a further aspect, there is provided a semiconductor device,comprising:

a substrate;

a fluorine-doped carbon film formed over said substrate;

an opening formed in said fluorine-doped carbon film;

a first metal film formed so as to cover at least a sidewall surface anda bottom surface of of said opening,

wherein there is formed, between said fluorine-doped carbon film andsaid first metal film, a second metal film so as to cover said sidewallsurface and bottom surface of said opening, there being formed afluoride film in said second metal film along an interface to saidsidewall of said opening where said fluorine-doped carbon film isexposed.

By modifying an exposed surface of a F-doped carbon film, F atomsexisting on the film surface are removed according to the presentinvention, and it becomes possible to suppress formation of volatilefluoride film at the interface, even in the case a barrier metal film,or the like, is formed on such a film surface. Thereby, it becomespossible to realize a reliable electric contact. By using a plasma CVDprocess that uses a microwave and characterized by low electrontemperature at the time of formation of the F-doped carbon film, andfurther by using a source gas having an F/C ratio, defined as a ratio ofF to C in the molecule, larger than 1 but less than 2, it becomespossible to achieve deposition of the desired F-doped carbon filmwithout adding a hydrogen gas. Because the F-doped carbon film thusformed does not contain hydrogen substantially in the film, and thereoccurs no problem of causing corrosion in the interconnection layer orother insulation layer when used for a multilayer interconnectionstructure. Further, because the F-doped carbon film of the presentinvention is substantially free from hydrogen, the film does not undergoetching when the foregoing modification processing is conducted by usingnitrogen radicals. Thereby, it becomes possible to conduct the desiredmodification processing stably and with good reproducibility.

Further, according to the present invention, it becomes possible, by wayof conducting the dry etching process of the F-doped carbon film and thedry cleaning process and further the metal film deposition process byusing a cluster-type substrate processing system, to conduct the processfrom the dry etching process to the metal film deposition processwithout exposing the substrate to the air, and it becomes possible toavoid absorption of water in the air to the highly reactive exposedsurface of the F-doped carbon film immediately after the dry etchingprocess.

Further, according to the present invention, it becomes possible, at thetime of depositing a metal film such as a Ta film on a F-doped carbonfilm, to avoid the problem of formation of volatile compound such as TaFand the interface between the interlayer insulation film and the barriermetal film becoming unstable, by interposing a second metal film thatforms a stable with the reaction with F.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a diagram explaining the problem with a conventionalfabrication process of a semiconductor device.

FIG. 2A is a diagram showing the construction of a microwave plasmaprocessing apparatus used with the present invention.

FIG. 2B is another diagram showing the construction of a microwaveplasma processing apparatus used with the present invention. microwaveplasma processing apparatus of FIG. 2.

FIG. 3 is a diagram showing a part of the microwave plasma processingapparatus of FIG. 2.

FIG. 4A is a diagram showing an electron temperature distribution in themicrowave plasma processing apparatus of FIG. 2.

FIG. 4B is a diagram showing an electron density distribution in themicrowave plasma processing apparatus of FIG. 2.

FIG. 5A is a first diagram showing the fabrication process of asemiconductor device according to a first embodiment of the presentinvention.

FIG. 5B is a second diagram showing the fabrication process of asemiconductor device according to a first embodiment of the presentinvention.

FIG. 5C is a third diagram showing the fabrication process of asemiconductor device according to a first embodiment of the presentinvention.

FIG. 5D is a fourth diagram showing the fabrication process of asemiconductor device according to a first embodiment of the presentinvention.

FIG. 5E is a fifth diagram showing the fabrication process of asemiconductor device according to a first embodiment of the presentinvention.

FIG. 5F is a sixth diagram showing the fabrication process of asemiconductor device according to a first embodiment of the presentinvention.

FIG. 5G is a seventh diagram showing the fabrication process of asemiconductor device according to a first embodiment of the presentinvention.

FIG. 5H is an eighth diagram showing the fabrication process of asemiconductor device according to a first embodiment of the presentinvention.

FIG. 6 is a diagram showing the construction of a cluster-type substrateprocessing apparatus according to a second embodiment of the presentinvention.

FIG. 7 is a diagram showing the construction of another cluster-typesubstrate processing apparatus used with the second embodiment of thepresent invention.

FIG. 8 is a diagram showing the construction of the semiconductor deviceaccording to a third embodiment of the present invention.

BEST MODE FOR IMPLEMENTING THE INVENTION First Embodiment

FIGS. 2A and 2B are diagrams showing the construction of a microwaveplasma processing apparatus 100 used with the first embodiment of thepresent invention, wherein FIG. 2A shows the microwave plasma processingapparatus in a cross-sectional view, while FIG. 2B shows theconstruction of a radial line slot antenna.

Referring to FIG. 2A, the microwave plasma processing apparatus 100includes a processing vessel 11 evacuated from plural evacuation ports11D and a stage 13 is provided in the processing vessel 11 of holding asubstrate 12 to be processed. In order to achieve uniform evacuation ofthe processing vessel 11, there is formed a ring-shaped space 11C aroundthe stage 13. Further, the plural evacuation ports 11D are formed incommunication with the space 11C with a uniform interval, and hence inaxial symmetry to the substrate to be processed. Thereby, it becomespossible to evacuate the processing vessel 11 uniformly via the space11C and the evacuation ports 11D.

On the processing vessel 11, there is provided a ceramic cover plate oflow-loss dielectric in the location corresponding to the substrate 12held on the stage 13 for processing, via a seal ring 16A as a part ofthe outer wall of the processing vessel 11, such that the ceramic coverplate 17 faces the substrate 12 to be processed.

The cover plate 17 is seated upon a ring-shaped member provided on theprocessing vessel via the foregoing seal ring 16A, while the ring-shapedmember 14 is provided with a ring-shaped plasma gas passage 14Bcorresponding to the ring-shaped member 14 in communication with aplasma gas supply port 14A. Further, the ring-shaped member 14 is formedwith plural plasma gas inlets 14C communicating with the plasma gaspassage 14B in axial symmetry to the substrate 12 to be processed.

Thus, the plasma gas such as Ar, Kr, Xe, H₂, and the like, supplied tothe plasma gas supply port 14A, are supplied to the inlets 14C via theplasma gas passage 14B and is released from the inlets 14C to a space11A right underneath the cover plate 17 inside the processing vessel 11.

On the processing vessel 11, there is further provided, over the coverplate 17, a radial line slot antenna 30 having a radiation plane shownin FIG. 2B with a separation of 4-5 mm from the cover plate 17.

The radial line slot antenna 30 is seated upon the ring-shaped member 14via a seal ring 16B and is connected to an external microwave source(not shown) via a coaxial waveguide 21. Thereby, the radial line slotantenna excites the plasma gas released to the space 11A by themicrowave from the microwave source.

The radial line slot antenna 30 comprises a flat, disk-shaped antennabody 22 connected to an outer waveguide 21A of the coaxial waveguide 21and a radiation plate 18 formed on an opening of the antenna body 22 andformed with a large number of slots 18 a and slots 18 b perpendicularthereto as showing in FIG. 2B, wherein a phase retardation plate 19 of adielectric plate of constant thickness is inserted between the antennabody 22 and the radiation plate 18. Further, a central conductor 21B ofthe coaxial waveguide 21 is connected to the radiation plate 18, and acooling block 20 including a coolant passage 20A is provided on theantenna body 22.

With the radial line slot antenna 20 of such a construction, themicrowave fed from the coaxial waveguide 21 spreads as it is propagatedin the radial direction between the disk-shaped antenna body 22 and theradiation plate 18 and thereby experiences wavelength compression as aresult of the action of the phase retardation plate 19. Thus, by formingthe slots 18 a and 18 b in a concentric manner in correspondence to thewavelength of the microwave propagating in the radial direction, itbecomes possible to radiate a plane wave of circular polarization in adirection substantially perpendicular to the radiation plate 18.

By using such a radial line slot antenna 30, there is formed uniformhigh-density plasma in the space 11A right underneath the cover plate17. Because the high-density plasma thus formed is characterized by lowelectron temperature, and because of this, there is caused littledamages in the substrate 12 to be processed. Further, there is caused nometal contamination originating from the sputtering of the chamber wallof the processing vessel 11.

With the plasma processing apparatus 100 of FIGS. 2A and 2B, there isformed a conductive structure 24 inside the processing vessel 11 betweenthe cover plate 17 and the substrate 12 to be processed such that theconductive structure is formed with a large number of nozzles 24B thatrelease a processing gas supplied from an external processing gas source(not shown) via the processing gas passages 23 and 24A formed in theprocessing vessel 11, where each of the nozzles 24B releases theprocessing gas thus supplied to a space 11B between the conductivestructure 24 and the substrate 12 to be processed. Thus, the conductivestructure 24 functions as a processing gas supplying part. Thereby, itshould be noted that the conductive structure 24 constituting theprocessing gas supplying part is formed with openings 24C betweenadjacent nozzles 24B and 24B as shown in FIG. 3 with a size that allowsefficient passage of the plasma formed in the space 11A to the space 11Bby way of diffusion.

FIG. 3 shows the processing gas supplying part 24 in a bottom view.

As can be seen from FIG. 3, the nozzles 24B are formed at the side ofthe processing gas supplying part 24 facing the substrate 12, not in theside that faces the cover plate 17.

Thus, the processing gas released from the processing gas supplying part24 to the space 11B in the plasma processing apparatus 100 of FIGS. 2Aand 2B via the nozzles 24B is excited by the high density plasma formedin the space 11A, and a uniform plasma processing is conducted on thesubstrate 12 to be processed efficiently at high speed, without damagingthe substrate and the device structure on the substrate, and withoutcontaminating the substrate. On the other hand, the microwave radiatedfrom the radial line slot antenna 30 is blocked by the processing gassupplying part 24 of a conductive body and there occurs no damaging ofthe substrate 12 to be processed by the microwave thus emitted from theradial line slot antenna 30.

With the substrate processing apparatus of FIGS. 2A and 2B, the spaces11A and 11B constitutes the processing space, wherein, in the case theprocessing gas supplying part 24 of FIG. 3 is provided, excitation ofplasma occurs primarily in the space 11A and film formation by theprocessing gas takes place primarily in the space 11B.

FIG. 4A shows the distribution of the electron temperature formed in theprocessing space of the plasma processing apparatus of FIGS. 2A and 2Bthat includes the space 11A and 11B, for the case the processingpressure in the processing vessel 11 is set to about 67 Pa (0.5 Torr) byintroducing an Ar gas from the plasma gas inlet 14C and by feeding amicrowave of 2.45 GHz or 8.3 GHz to the radial line slot antenna 30 withthe power density of 1.27 W/cm². In FIG. 4A, it should be noted that thevertical axis represents the electron temperature while the horizontalaxis represents the distance as measured from the bottom surface of thecover plate.

Referring to FIG. 4A, the electron temperature becomes maximum in theregion immediately underneath the cover plate 17 and takes the value ofabout 2.0 eV in the case the microwave frequency is 2.45 GHz and thevalue of about 1.8 eV in the case the microwave frequency is 8.3 GHz,while, in the so-called diffusion plasma region separated from the coverplate 17 by 20 mm or more, it can be seen that the electron temperatureis generally constant and takes the value of 1.0-1.1 eV.

Thus, with the microwave plasma processing apparatus 100, it is possibleto form the plasma of extremely low electron temperature, and it becomespossible to conduct the process that requires low energy by using suchplasma of low electron temperature.

FIG. 4B shows the distribution of the plasma electron density caused inthe processing vessel 11 in the plasma processing apparatus 100 of FIGS.2A and 2B.

Referring to FIG. 4B, the illustrated example is the result for the casethe processing pressure in the processing vessel 11 is set to about 67Pa (0.5 Torr) by introducing an Ar gas from the plasma gas inlet 14C anda microwave of 2.45 GHz or 8.3 GHz is fed to the radial line slotantenna 30 with the power density of 1.27 W/cm², wherein it can be seenthat a very high plasma density of 1×10¹² cm⁻² is realized up to thedistance of 60-70 mm from the bottom surface of the cover plate 17 inany of the case in which the frequency is 2.45 GHz and the case in whichthe frequency is 8.3 GHz.

Thus, with the present embodiment, it is possible to form a F-dopedcarbon film on the substrate 12 to be processed, by setting the positionof the processing gas inlet 24 at the distance within 60 mm from thebottom surface of the cover plate 17 such that the foregoing plasmaelectron density of 1×10¹² cm⁻² is realized and further by exciting theplasma in the processing vessel 11A by introducing the Ar gas from theplasma gas inlet 14C and by feeding the microwave of 1-10 GHz from theantenna, and further by introducing a C₅F₈ gas to the processing space11B from the processing gas inlet 24 in this state.

FIGS. 5A-5H are the diagrams showing the fabrication process of asemiconductor device according to a first embodiment of the presentinvention.

Referring to FIG. 5A there is formed a cap layer 43 of an SiN film orSiOC film on the Si substrate 41, on which an insulation film 42 ofSiO₂, SiOC, or other low-K dielectric film is formed, and a F-dopedcarbon film 44 is formed on the cap layer 43 in the plasma processingapparatus 100 explained with reference to FIGS. 2A and 2B by introducinga C₅F₈ source gas to the processing space 11B from the processing gassupplying part 24. Such deposition of the F-doped carbon film 44 can beconducted by setting the substrate temperature to 250° C. and bysupplying an Ar gas to the space 11A right underneath the cover plate 17from the plasma gas supplying part 14C under the pressure of about 100Pa and further by supplying the microwave of the frequency of 2.45 GHzfrom the radial line slot antenna 30 with the power density of 2.0W/cm². In the illustrated example, an interconnection pattern 42A of Cu,or the like, is embedded in the low-K insulation film 42.

In the case of forming a F-doped carbon film 44 by a plasma CVD processthat uses an ordinary plasma processing apparatus of parallel plate type(CCP type) or ICP type, there is a need of adding a hydrogen gas forremoving the F radicals formed as a result of dissociation of the sourcegas molecules from the system, and thus, it is inevitable that theobtained F-doped carbon film contains a large amount of hydrogen.Contrary to this, in the case of causing dissociation of fluorocarbonsource having the F/C ratio, defined as the ratio of the number of Fatoms to the number of C atoms in a molecule, is larger than 1 but lessthan 2, such as the C5F8 source gas, in the plasma processing apparatusof FIGS. 2A and 2B by the microwave supplied from the radial line slotantenna 30, it is possible to form a desired F-doped carbon film 44without adding a hydrogen gas. Thus, the F-doped carbon film 44 formedin such a manner is a film substantially free from hydrogen.

After forming the F-doped carbon film 44 in this way, the step of FIG.5B is conducted next, in which a hard mask film 45 of SiCN, SiN or SiO₂is formed on the F-doped carbon film 44 by using the same plasmaprocessing apparatus 100. Further, in the step of FIG. 5C, a resistpattern 46 having an opening 46A is formed on the hard mask film 45 byan ordinary photolithographic process. In the case of forming the hardmask film 45 by an SiCN film in the plasma processing apparatus 100,trimethyl silane is supplied from the processing gas supplying part 24to the processing space 11B as a source gas, and plasma containingnitrogen radicals is excited by supplying an Ar gas and a nitrogen gasto the space 11A right underneath the cover plate 17 from the plasma gassupplying part 14C. In a typical example, deposition of such an SiCNfilm 45 can be conducted by setting the substrate temperature to 350° C.and supplying the microwave of the 2.54 GHz frequency from the radialline slot antenna 30 under the pressure of about 200 Pa with the powerdensity of 1.0 W/cm².

Further, in the step of FIG. 5C, a hard mask pattern 45A is formed bypatterning the hard mask layer 45 while using the resist pattern 46 as amask, and in the step of FIG. 5D, the F-doped carbon film 44 underneaththe hard mask pattern 45 is patterned while using the hard mask pattern45A as a mask. As a result, there is formed an opening corresponding tothe resist opening 46A in the F-doped carbon film 44 such that theinterconnection layer 42A is exposed at the bottom of the opening 44A.

With the present embodiment, the structure of FIG. 5D is introducedagain into the plasma processing apparatus 100 of FIGS. 2A and 2B in thestep of FIG. 5E, and nitrogen radicals N* are formed by introducing amixed gas of Ar and nitrogen into the space 11A right underneath thecover plate 17 from the plasma gas inlet 14C.

With the step of FIG. 5E, the nitrogen radicals N* thus formed are usedto process the substrate 41 in the processing space 11B, such that thereis caused decoupling of the F atoms existing on the surface of theF-doped carbon film 44 exposed at the sidewall surface of the opening44A. Further, as a result of such nitrogen radical processing, there isa possibility that a modified layer is formed on the exposed surface ofthe F-doped carbon film 44 by coupling of nitrogen.

After the step of FIG. 5E, a Ta film 47 is formed on the structure ofFIG. 5E in the step of FIG. 5F with the present embodiment as a barriermetal film, such that the Ta film 47 covers the surface of the hard maskfilm 45 and the exposed sidewall surface of the F-doped carbon film 44and the surface of the interconnection pattern exposed at the bottom ofthe opening 44A continuously.

Because the F atoms are removed from the surface of the F-doped carbonfilm 44 exposed at the sidewall surface of the opening 44A in the stepof FIG. 5E with the present embodiment, there occurs no substantialformation of volatile TaF even in the case the Ta film 47 is formed soas to cover the sidewall surface, and the Ta film 47 has excellentadherence. Further, because the F-doped carbon film is substantiallyfree from hydrogen, release of HF from the film 44 is suppressed alsoeffectively.

Meanwhile, in the case the conventional F-doped carbon film is processedby the nitrogen radicals as in the step of FIG. 5E, it is common thatthere occurs severe etching, and it is extremely difficult to conduct amodification process, while there is a possibility that this problem iscaused by the reaction of the hydrogen contained in the F-doped carbonfilm with the nitrogen radical to form an N—H group. Contrary to this,the F-doped carbon film of the present invention is film substantiallyfree from hydrogen, and no such a problem takes place.

After the step of FIG. 5F, a Cu layer 48 is formed on the structure ofFIG. 5D in the step of FIG. 5G typically by a seed layer forming processconducted by a CVD process and an electrolytic plating process so as tofilm the opening 44A. Further, in the step of FIG. 5H, a part of the Culayer 48 including the barrier metal film 47 and the hardmask film 45 isremoved, and a structure is obtained such that a Cu pattern 48Aconstituting a Cu interconnection pattern or plug is formed in theF-doped carbon film 44 via a Ta barrier metal film 47.

As explained before, the structure thus obtained is stable and highlyreliable contact is realized.

Second Embodiment

In the first embodiment of the present invention explained before, thereis a need of conducting a cleaning process after the dry etching processof FIG. 5D for removing impurities deposited on the sidewall surface ofthe opening 44A, and thus, the cleaning process has been conducted bytaking out the structure from the dry etching apparatus.

However, in the case the cleaning process of the structure of FIG. 5D isconducted in the air, water vapor in the air is adsorbed upon thesidewall surface of the opening 44A, and there is a possibility thatformation of HF is caused.

Thus, with the present embodiment, all the process steps from FIG. 5D toFIG. 5F are conducted by using a cluster-type substrate processingsystem 60 shown in FIG. 6.

Referring to FIG. 6, the cluster-type substrate processing apparatus 60comprises a vacuum transfer chamber 61 coupled with a load-lock chamber62 for loading in and out a substrate and provided with a transfer robottherein, a dry etching chamber 63 coupled to the vacuum transfer chamber61, a modification processing chamber 64 coupled to the vacuum transferchamber 61 and conducing modification processing of FIG. 5E, asputtering chamber 65 coupled to the vacuum transfer chamber 61 andconducting deposition of Ta film of FIG. 5F, and a cleaning chamber 66coupled to the vacuum transfer chamber 61 and conducting dry cleaning tothe structure of FIG. 5D, wherein each of the dry etching chamber 63 andthe modification chamber 64 is provided with a plasma processingapparatus 100 of the construction identical to the one explained withreference to FIGS. 2A and 2B.

Thus, after the step of FIG. 5C, the substrate 41 is introduced, afterremoving the resist pattern 46 by an ashing process, or the like, fromthe load-lock chamber 62 to the dry etching chamber 63 via the vacuumtransfer chamber 61, and the dry etching process of FIG. 5D isconducted.

With this dry etching process, an Ar gas is introduced into the space11A from the plasma gas inlet 14C and an etching gas such as N₂+H₂ isintroduced into the processing space 11B from the processing part 24 inthe plasma processing apparatus 100 provided in the dry etching chamber63, and the desired dry etching is conducted by introducing a microwaveto the space 11A from the radial line slot antenna 30 via the microwavewindow 17 while applying a high frequency bias to the stage 13 from thehigh frequency source 13A.

After the dry etching process of FIG. 5D, the substrate 41 underprocessing is transported to the modification chamber 64 via the vacuumtransfer chamber 61, and the modification processing of FIG. 5E isconducted.

With this modification processing, an Ar gas and a nitrogen gas areintroduced into the space 11A from the plasma gas inlet 14C with theplasma processing apparatus 100 provided in the modification chamber 64,and the modification processing of FIG. 5E is conducted by introducing amicrowave to the space 11A via the microwave window 17 from the radicalline slot antenna 30.

Further, after the modification processing of FIG. 5E, the substrate 41under processing is transferred to the dry cleaning chamber 66 via thevacuum transfer chamber 61, and a dry cleaning processing is conductedby using NF₃, F₂, CO₂ or a chlorofluorocarbon family gas.

The substrate 41 thus completed with the dry cleaning processing in theprocessing chamber 66 is further forwarded to the sputtering processingchamber 65 via the vacuum transfer chamber 61, and the Ta barrier metalfilm 47 is formed by the process of FIG. 5F.

After the step of FIG. 5F, the substrate 41 under processing is returnedto the load-lock chamber 62 via the vacuum transfer chamber 61.

FIG. 7 shows the construction of another cluster-type substrateprocessing system 80 that is used together with the substrate processingsystem 60 of FIG. 6 for formation of the cap film 43, the F-doped carbonfilm 44 and the hard mask film 45.

Referring to FIG. 7, the cluster-type substrate processing apparatus 80comprises a vacuum transfer chamber 81 coupled with a load-lock chamber82 for loading in and out a substrate and provided with a transfer robottherein, a deposition chamber 83 coupled to the vacuum transfer chamber81 and used for the formation of the cap film 43, a deposition chamber84 coupled to the vacuum transfer chamber 81 and used for the formationof the F-doped carbon film 44, and a deposition chamber 85 coupled tothe vacuum transfer chamber 81 and used for formation of the hard maskfilm 45, wherein each of the deposition chambers 83, 84 and 85 isprovided with the plasma processing apparatus 100 identical inconstruction with that explained with reference to FIGS. 2A and 2B.

Thus, after formation of the insulation film 42 and the interconnectionpattern 42A, the substrate 41 under processing is transported to thedeposition chamber from the load-lock chamber 82 via the vacuum transferchamber 81, the cap film 43 is formed on the insulation film 42 bysupplying an Ar gas and a nitrogen to the space 11A right underneath thecover plate 17 from the plasma gas supplying part 14C and by supplying aSi-containing gas such as trimethyl silane or SiH4 to the processingspace 11B from the processing gas supplying part 24 in the plasmaprocessing apparatus 100 provided in the processing chamber 83, andfurther by exciting microwave plasma by feeding a microwave to the space11A from the radial line slot antenna 30 via the cover plate 17.

After formation of the cap layer 43, the substrate 41 under processingis transferred to the deposition chamber 84 from the deposition chamber83 via the vacuum transfer chamber 81, and in the plasma processingapparatus 100 in the deposition chamber 84, an Ar gas and a nitrogen gasare supplied from the plasma gas supplying part 14C to the space 11Aright underneath the cover plate 17, and the F-doped carbon film 44 isformed on the cap layer 43 by supplying a fluorocarbon source gas havingthe F/C ratio in the molecule larger than 1 but less than 2, such asC₅F₈, into the processing space 11B from the processing gas supplyingpart 24, and further by exciting microwave plasma in the space 11A bysupplying a microwave in the space 11A from the radial line slot antenna30 via the cover plate 17. As explained previously, it is not necessaryto add a hydrogen gas to the source gas in the formation step of theF-doped carbon film, and thus, the obtained F-doped carbon film 44 issubstantially free from hydrogen.

After such formation of the F-doped carbon film, the substrate 41 underprocessing is transported to the deposition chamber 85 from thedeposition chamber 84 via the vacuum transfer chamber 81, and the hardmask film 45 is formed on the F-doped carbon film in the plasmaprocessing apparatus 100 in the deposition chamber 85 by supplying an Argas and a nitrogen gas to the space 11A right underneath the cover plate17 from the plasma gas supplying part 14C and by supplying aSi-containing source gas such as trimethyl silane or SiH₄ to theprocessing space 11B from the processing gas supplying part 24, andfurther exciting microwave plasma in the space 11A by supplying amicrowave to the space 11A from the radial line slot antenna via thecover plate 17.

The substrate 41 thus formed with the hard mask film 45 is returned tothe load-lock chamber via the vacuum transfer chamber 81 and isforwarded to the resist process and photolithographic process of FIG.5C.

Thus, by using the cluster-type substrate processing system 80 of FIG.7, it becomes possible to form the hard mask film 45 on the F-dopedcarbon film 44 without exposing the F-doped carbon film 44 to the air,and it becomes possible to avoid water adsorption to the surface of thefilm 44.

Third Embodiment

FIG. 8 is a diagram showing the construction of a semiconductor device120 according to a third embodiment of the present invention, whereinthose parts of FIG. 8 explained previously are designated by the samereference numerals and the description thereof will be omitted.

Referring to FIG. 8, the illustrate shows the state after the Ta barriermetal film 47 is formed but before the Cu layer 48 of FIG. 5G is formedexplained previously with reference to FIG. 5F, wherein it should benoted that, with the present embodiment, an Al film 49 is depositedbetween the surface of the hard mask film 45 or the F-doped carbon filmexposed at the opening 44A and the Ta barrier metal film 47.

By providing the Al film 49, the Ta barrier film 47 is separated fromthe F-doped carbon film 44 and the problem of formation of volatile TaFas a result of reaction of the barrier film 47 with F is avoided.Because Al forms stable AlF when reacted with F, it can be seen thatthere is formed an AlF layer in the construction of FIG. 8 in the partof the Al film 49 that forms an interface contacting with the F-dopedcarbon film surface. Further, there is formed an Al-Cu alloy in the partof the Al film 49 that corresponds to the bottom of the opening 44Awhere contact to the Cu interconnection pattern 42A is to be made.

The Al film 49 is typically formed by a sputtering process, while it isalso possible to form by an ALD process or CVD process.

For the film 49, any metal film that forms a stable compound whenreacted with F can be used. For example, it is possible to use Ru, Ni,Co, Pt, Au, Ag, or the like, in addition to Al.

With the present embodiment, too, it is preferable to form the F-dopedcarbon film 33 by using the fluorocarbon source in which the F/C ratiois larger than 1 but smaller than 2 for avoiding the formation ofcorrosive HF and by using the microwave plasma processing apparatus 100explained with reference to FIGS. 2A and 2B.

Thereby, it is also possible to use C₃F₄, C₄F₆, or the like, in additionto C₅F₈, for the fluorocarbon source.

Further, modification of the fluorine-doped carbon film of the presentinvention is not limited to nitrogen or Ar explained before, but it isalso possible to conduct by using in the radicals containing any of Kr,C, B and Si.

While the present invention has been explained heretofore with referenceto preferred embodiments, the present invention is by no means limitedto such specific embodiments, and various variations and modificationscan be made within the scope of the invention in patent claims.

INDUSTRIAL APPLICABILITY

The present invention is generally applicable to the method of formingan insulation film and is applicable particularly to the film formingmethod of a F (fluorine)-doped carbon film, the fabrication method of asemiconductor device that uses such a forming method of fluorine-dopedcarbon film, a semiconductor device fabricated with such a method, andfurther to a substrate processing system for fabrication of such asemiconductor device.

1. A method of fabricating a semiconductor device, comprising the stepsof: depositing a fluorine-doped carbon film on a substrate by a plasmaCVD process that uses a source gas that contains C and F in a moleculethereof; forming an opening in said fluorine-doped carbon film by a dryetching process; and depositing a first metal film so as to cover asidewall surface and a bottom surface of said opening; wherein there isprovided, after said step of forming said opening but before said stepof depositing said first metal film, a step of forming a stable compoundby depositing a second metal film that reacts with F, such that saidsecond metal film covers at least said sidewall surface and bottomsurface of said opening.
 2. The method of fabricating a semiconductordevice as claimed in claim 1, wherein said second metal film is selectedfrom a group consisting of Al, Ru, Ni, Co, Pt, Au and Ag.
 3. Thesemiconductor device, comprising: the substrate; the fluorine-dopedcarbon film formed over said substrate; the opening formed in saidfluorine-doped carbon film; the first metal film formed so as to coverat least the sidewall surface and the bottom surface of said opening,wherein there is formed, between said fluorine-doped carbon film andsaid first metal film, the second metal film so as to cover saidsidewall surface and bottom surface of said opening, there being formedthe fluoride film in said second metal film along the interface to saidsidewall of said opening where said fluorine-doped carbon film isexposed, and wherein the semiconductor device is fabricated by themethod as claimed in claim
 1. 4. The semiconductor device as claimed inclaim 3, wherein said opening exposes a copper interconnection patternat a bottom part thereof, and wherein said second metal film forms analloy containing Cu along an interface to said copper interconnectionpattern.